Well, there are more than two links in the article. Many of them lay out methods that would detect fraud if it were happening. Nobody is "pretending", we have investigated and concluded that it is not happening. For example:
http://apr.sagepub.com/content/42/2/311"Although voter ID laws have become a hot topic of political debate, existing scholarship has failed to produce conclusive evidence concerning the existence or frequency of electoral fraud, especially the type of fraud that would be prevented by photo identification laws and signature verification protocols for voting by mail. We propose a new method of measuring election fraud, especially identity fraud, that is superior to previous measurement efforts because it measures actual instances of fraud rather than waiting for conclusive proof of fraud produced in a criminal prosecution. We test our method in multiple jurisdictions, including two known cases of electoral fraud, and we find no additional cases of fraud. We speculate that public access to voting and registration records play an important role in preventing this type of election fraud, suggesting that these practices are perhaps more important than voter ID laws in preventing election fraud."
Requiring an ID for alcohol is not unreasonable because there is no constitutional right to be able to purchase it. I imagine there are some gun control opponents who argue that requiring an ID to buy a gun is unconstitutional, but there is ample evidence that not requiring an ID causes immense societal problems, and infringes on other people's constitutional rights. This is not true of voting, as you can see in that article.
